The present invention relates to volumetric pumps intended in particular for rubber mixes and, more particularly, to gear pumps.
It is known to use volumetric gear pumps for high-viscosity plastics materials such as the one described in Greenstreet et al. U.S. Pat. No. 5,120,206. A pump of this type uses a gear system comprising a motorised driving gear wheel, “driving wheel”, and a second wheel engaged with the first and driven in rotation thereby, and also a feed screw which makes it possible to force-feed said pump with high-viscosity plastics material.
The rubber mixes also have a very high viscosity, which causes a very great resisting torque on the driving wheel. This resisting torque is all the greater since it is desired to achieve high flow rates by increasing the width of the gear wheels. These difficulties are so great that, in applications of gear pumps to rubber, frequent breakage of the gear wheels is observed.
Furthermore, the achieving of a high flow rate for the rubber mixes is limited by the thermal aspect, because the increase in flow rate, which is mainly a function of the increase in speed of rotation of the gear wheels, is accompanied by a large increase in the temperature of the rubber mixes; now, this temperature must be both controlled and in particular its increase limited in order to avoid early vulcanisation of these mixes.